Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods, but fortified breakfast cereals are a readily available source of vitamin B12 with high bioavailability for vegetarians . Some nutritional yeast products also contain vitamin B12. Fortified foods vary in formulation, so it is important to read product labels to determine which added nutrients they contain.